The Telescope

Spitzer's telescope is a lightweight reflector of Ritchey-Chrétien design, with a mirror measuring 85 centimeters in diameter. It
weighs less than 50 kg (110 pounds), and is designed to operate at an extremely
low temperature.

All of its parts, except for the mirror supports, are made
of beryllium, which is extremely light but very strong. Beryllium works
especially well in the construction of infrared telescopes, because it has a
low heat capacity at very low temperatures, meaning that it is very easy to
cool down quickly. It is important for as much of the telescope as possible to
be built from a single type of material, because different materials expand and
contract by different amounts as they heat up and cool down. Building the
telescope out of different materials could cause it to flex out of shape as it
changes temperature, putting extra stress on the joints and causing the
telescope to go out of focus.

The telescope is attached to the top of the cryostat, which
keeps the scientific instruments very cold.

The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory. This website is maintained by the Spitzer Science Center, located at IPAC on the campus of the California Institute of Technology.